I am using the Katana conversion from e-bay, $9.00, and I had to buy a new cable. Any of the oil cooled gsxrs, with cable clutch should work, like the older GSXR 750s.
About horsepower, you need to keep in mind, that Horsepower is a caculation, based on torque. My bike makes 155 hp, 81.4 torque at 10,000 rpms. I could advance the cam timing so that it makes the 81.4 torque at 9,500 and it would make 147 horse power, and it would probabley be just as quick in the quarter even with less hp, may even be a little quicker in the 1/8. We should never get hung up on hp numbers.
My last dragbike was a GSXR with a 1216 kit, stock head, cams and carbs, but was set up just for the 1/4 mile, ran 9.60s at 133/135 mph, with less hp.
Setup gives you good ETs, Horsepower will give you good MPH